1. Field of the Invention
The present invention relates to a data processing apparatus for arc welding.
2. Description of the Related Art
A robot system in which an arc welding torch is mounted on an arm end portion of a robot to perform arc welding is known. In this type of arc welding robot system, one typical technique for teaching the robot a welding operation is a so-called playback teaching technique. In the playback teaching technique, generally, the actual robot is operated by jog-feeding in a manual mode, to move the welding torch along a welding line on a workpiece, and to make the robot store the position and orientation of the arm at several predetermined teaching points. The orientation of the arm is set in such a manner that the welding torch appropriately exhibits a target angle (or a work angle (JIS)) and a lead angle (or a travel angle (JIS)) relative to the welding line at each teaching point. The robot executes a welding operation program describing the position and orientation data at the teaching points, so as to perform the welding work. It should be noted that both the “work angle” and the “travel angle” are angle data representing the geometric placement of the arc welding torch with respect to the workpiece (or the welding line) during the welding operation, which will be described, later, in more detail.
Another typical teaching technique uses an off-line programming system. In the off-line programming system, information about the robot, welding torch, workpiece, surrounding objects and so on, is given by an off-line location (i.e., at a location away from the actual operating environment) to a processing apparatus, so that a work-cell is defined in the processing apparatus on the basis of the information. The work-cell is composed of the reconstruction of an actual job site in a virtual space. The position and orientation data of the robot at the teaching points, which must be described in the welding operation program, are determined based on the position and orientation taken by the virtual robot operating in the work-cell. The orientation of the robot is also determined in such a manner that the virtual welding torch defined in the work-cell exhibits appropriate work and travel angles with respect to the virtual workpiece. Then, the welding operation program describing the position and orientation data at the teaching points is transferred to a robot controller, to control the actual robot, so as to perform the welding work.
In the playback teaching technique described above, the position and orientation of the arm are adjusted visually while the actual robot is operated by jog-feeding, so that it is generally difficult to perform the appropriate teaching in a short time and a skilled operator is required. In particular, in order to accurately set the work angle and the travel angle, which are important conditions influencing the welding quality, there is a problem in that the operation, including jog-feeding, teaching and program executing, should be done by repeated trial and error, and the number of processing steps are thus increased significantly.
On the other hand, in the off-line programming teaching technique described above, an error typically exists between an equipment layout defined in the work-cell in the processing apparatus and an actual equipment layout, so that, when the welding operation program provided in an off-line mode is actually executed at the job site, the welding operation program often cannot be used in its original form. Therefore, in this case, the position and orientation data at the teaching points have to be corrected as required. However, because the work angle and travel angle are changed due to the data correction, it is also necessary to perform the programming work by repeated trial and error. As a result, the problem of the increased number of processing steps cannot be solved in the off-line programming teaching technique, just as in the playback teaching technique.
One of the reasons for the above-described problems in conventional teaching techniques is that, in the conventional programming work, welding conditions including the work angle and the travel angle cannot be described directly in the welding operation program. Further, the operator can grasp directly the position and orientation of the robot at the teaching points from the welding operation program, but cannot grasp the work angle and travel angle of the welding torch, corresponding to the position and orientation at the teaching points, unless the operator calculates, as another step, the work angle and the travel angle from the position and orientation data. Therefore, for example, even if optimal welding conditions including the work angle and the travel angle are previously recognized, it is necessary for the operator to calculate the position and orientation data of the robot on the basis of the optimal welding conditions, and to provide or correct the welding operation program by using the calculated position and orientation data. Thus, in the conventional arc welding robot system, there is a problem in that a significant time is consumed for the provision and the correction of the welding operation program.